Analyzing earth formations



June 26, 1945. H. F. STURGIS ANALYZING EARTH FORMATIONS Filed May 29, 1941 2 Sheets-Sheet l June 26, 1945. H. F. STURGIS ANALYZING EARTH FORMATIONS Filed May 29, 1941 Sheets-Sheet 2 n w p u a ea a v 0Q 0 a onu n p a u u v ,a uau oo i110 7" 7zej,

Patented June 26, 1945 ANALYZING EARTH FORMATIONS Henry F. Sturgis, Tulsa, Okla., asslgnor to Stanolind Oil and Gas Company, Tulsa, Okla., a

corporation of Delaware Application May 29, 1941, Serial No. 395,792

I 9 Claims.

This invention'relates to the analysis of earth formations and particularly to geochemical pros-' pecting and especially to geochemical well logging. This invention is particularly concerned with the determination of the hydrocarbon and water content of drill cuttings from subsurface formations.

It' has been found that the presence of various hydrocarbons or quasi-hydrocarbons in drill cuttings from subsurface formations or from surface soils is related to the presence of oil and gas deposists located in deeper strata far below. These hydrocarbons and quasi-hydrocarbons which,

serve as indicia of the petroleum deposits include gaseous, liquid and solid materials. The hydrocarbon content of samples of drill cuttings or surface soils is determined by analysis, these determinations being used in preparing a log or map to obtain an indication of the presence and location of oil and gas deposits.

In making a geochemical Well log, samples of the drill cuttings are taken at frequent vertically spaced intervals along a well bore, and the samples analyzed by any of various methods for various hydrocarbon or quasi-hydrocarbon constituents, and the results for the various samples are compared and plotted in order to obtain a log of the well which indicates the presence and location of oil and gas deposits in the deeper strata.

It is an object of my invention to provide a new and improved method and means for the recovery of hydrocarbons from drill cuttings. Another and more detailed object is to provide an im-' proved method and means for separating hydrocarbons from wet drill cuttings for geochemical well logging. A further object of my invention is to provide an improved method and means for determination of water in a wet sample of drill cuttings while ,recovering hydrocarbons therefrom, allowing all geochemical values to be reduced to a dry sample basis for comparison.

A still further object of my invention is to provide anew method and means whereby a larger percentage of the hydrocarbons present in drill cuttings, cores, surface soils, or other earth formations, can be recovered than has heretofore been possible. An additional advantage of my invention is the minimization of solvent evaporation during the absorption of hydrocarbons obtained from drill cuttings, cores, surface soils, and other earth formations. Other objects and advantages will become apparent as the description of my invention proceeds.

In the drawings:

Figure 1 is an elevation, partly in section, of one form of apparatus suitable for use in accordance with my invention; and

Figures 2, 3, 4, and 5 illustrate in elevation, partly in section, various forms of retorts and steam generators suitable for use with the absorption apparatus shown in Figure 1.

My invention will bedescribed with particular reference to the analysis of samples of drill cuttings but it should be understood that it is also applicable to the analysis of samples of surface soils taken from horizontally spaced survey stations in the course of a geochemical prospecting operation and it is likewise applicable to the analysis of cores taken from wells, including cores taken from oil and gas bearing strata and to the analysis of other earth formations todetermine hydrocarbons, water, or both.

Samples of drill cuttings or cores taken at selected spaced vertical points along a well bore can be transferred to sample jars which are tightly closed or sealed to prevent any evaporation loss. Heretofore it has usually been considered necessary or. desrable to air dry" the samples under more or less controlled conditions in order to obtain comparable values on a dry basis." Naturally under such conditions greater ordesser amounts of hydrocarbons are apt to be lost by evaporation, and although comparative values between samples from various pointsmight still be indicative of the relative amount of oil or gas present in the formation, evaporation losses are apt to vary widely, so that a truly comparative value cnnot be obtained. Determination of the actual amount of hydrocarbons present in the sample will supply much more accurate information relative to the hydrocarbon content of the deeper strata of earth formation. Also, the air dried samples are usually crushed to a grain size, which increases the loss of hydrocarbons by evaporation due to the additional surface exposed by the crushing.

According to my invention, a portion of the wet drill cuttings or core is weighed directly from the sample bottle into a retort without intermediate air drying or crushing. The hydrocarbons and water are then driven off by externally applied heat from a constant temperature bath, and the released hydrocarbons and water bubbled through a solvent or. absorbent which absorbs the hydrocarbons and condenses the water. To insure complete removal of the hydrocarbons from the sample, provisions are made to flush them from the sample and apparatus with steam.

The solvent with the hydrocarbons therein can then be separated from the water and condensed steam, and the hydrocarbon constituents ascertained by any one of a number of methods as,

'for example, by the refractive index method described in U. B. Patent No. 2,213,905 to Clark or the density method set forth in the co-pending application of. Thompson .Serial Number 388,411.

These particular methods of determining hydrocarbons from samples of earth formations are especially applicable in conjunction with the present invention, since they require no separation of the absorbed hydrocarbons from the solvent.

In the Clark method. a solvent of known refractive index is used to absorb the hydrocarbons, the solvent being chosen with a refractive index substantially different from that .of the hydrocarbons found in the samples. By comparing the refractive index of a standard volume of extracted hydrocarbon and solvent with similar solvent hydrocarbon mixtures from samples taken at other points, variations in hydrocarbon content can be easily plotted. On the other hand, if the quantity and nature of the absorbed hydrocarbons is of particular interest, this can be deter-.- mined from the solvent-hydrocarbon mixture by optical titration, using another solvent having a radically different refractive index. The Thompson method of determining hydrocarbons from samples of earth formations is based on variations in relative density, the solvent being of known density and the deviation therefrom caused by the presence of the absorbed hydrocarbons bein a measure of the hydrocarbon content and .the nature thereof.

Other methods of analysis include separation of the hydrocarbons from the solvent, and their measurement, with or without determination of their make-up, e. g. by fractional distillation using liquid air; combustion analysis; Raman spectra; infrared spectra; mass spectra; or other methods known to the art. These, however, while included within the scope of this application, require considerably greater technique inseparating the hydrocarbons from the solvent without loss of various constituents.

Referring now to Figure 1, sample retortilll is fitted with a male Joint within shoulders |2 adaptedto hold a mercury seal I3. From one side of the base of retort In there extends a water delivery tube l4 equipped with stock cocks I5 and I8 with a reservoir |4a therebetween and surmounted by a graduated measuring cylinder H. A thermostatically controlled bath I8 is supplied to surround and heat the lower part of retort l0 containing the sample. The lower portion of water delivery tube I4 is also encompassed by the bath l8 when the bath is in the elevated position shown in dotted lines.

Male joint II on retort l0 fits into the female joint I! of delivery tube which extends from retort III to the base of absorption column 2|. Delivery tube 20 is also equipped, if desired, with a T 22 having a three-way stopcock 23 therein, and a solventtrap 24, trap 24 being at a height sufllcient to prevent the overflow of solvent fro absorption cylinder-2| to retort l0. L

Absorption cylinder 2| can be filled throughout the lower portion of its length with packing material 25 which can consist of small lengths of glass rod or glass tubing, ceramic material, broken quartz, etc., or baflies or other means can be used, which will impede the upflow of materials entering from line 20 and cause increased contact between the absorption medium and the gaseous materials. The upper part of absorption column 2| is provided with markings 26 to indicate the volume. Column 2| is also surrounded by a water Jacket 21 throughout the greater part of its length, water or other cooling medium entering through line 28 and discharging through line 29. By this means, the hot products from line 20 are cooled and condensed as well as absorbed in the absorption medium and the escape of any considerable quantity of liqueflable material is thereby prevented. An escape line 20 is provided for uncondensed gases. An absorption medium, which can suitably be carbon tetrachloride, carbon disulflde, dibromoethane, tetrabromocthane, benzene, cyclohexane, normal pentane, light naphtha, etc., is provided from a source 3| .through line 22 leading'to column 2|, line 22 being containing absorbed material, as well 'as condensed water and steam, can be withdrawn from column 2| by opening stopcock 24 in line 26, the liquid being collected in a container 36.

In operation a weighed amount of drill cutting sample is placed in retort Ill and constant temperature bath I8 elevated to surround the major portion of the retort as well as line H from measuring cylinder Stopcocks I5 and I6 are closed and stopcock 22 turned to form a single passage from retort Hi to absorption column 2|. Sufllcient absorption medium, for example carbon tetrachloride, is added to column 2| by opening stopcock 33 (stopcock 34 being closed) to flli column 2| at least as high as the markings 26. The temperature of the constant-temperature bath is regulated to provide temperatures up to 600 F. or higher. although temperatures of from about 550 to about 600 F. will effectively remove all of the moisture and most of the hydrocarbons from the sample. Temperatures as low as about 250 F. are acceptable, however, since the steam will flush out all of, the hydrocarbons from the sample at this temperature. When substantially all of the moisture and hydrocarbons, as well as any other volatile materials, have been removed from the sample, a measured amount of water is admitted from measuring cylinder H by opening valve I6 whichpermits reservoir Ha to be filled. This substantially total removal of hydrocarbons is determined for any group of samples by heating one sample for varying lengths of time to a fixed temperature, and measuring the relative completeness of the desorption process with time. Then all samples are heated for the length of time found to give substantially complete desorption. Typically this time is about one half hour at 550 F. By closing valve l6 and opening valve I5, water from reservoir |4a will flow through line M in heated bath l8 to retort l0. As the water passes in the tube through the hot bath to retort l0 it is converted into steam which rises through the sample in retort Ill, sweeping out the hydrocarbon vapors through the retort and tubing into the absorption column.

Since the water both from the sample and from the condensed steam will be collected above the carbon tetrachloride in column,2|, and since the amount of water converted to steam can be ascertained from measuring cylinder II, it is a simple matter tosubtract the amount of water collected above the carbon tetrachloride from the amount added from measuring cylinder II to determine the amount of water originally in the sample.

tort bottom and instantly become vaporized, and pass upward through a perforated plate to sweep all vapors from the sample and the retort.

It is recognized that in order to add water from a cylinder such as a graduate, suflicient head must be provided to overcome the pressure exerted by the carbon tetrachloride. Ordinarily it is a simple matter to raise a water storage cylinder to a suflicient-elevation to provide this required head. n the other hand, if the elevation is so great that reading thewater level in the storage cylinder I1 is diiflcult, the alternative means. From the weight of the sample'and the amount of moisture .determined therein, it is possible to determine the percentage of hydrocarbons present in the wet ,drill cuttings on a dry basis," or if desired, on dried samples, since such samples can be analyzed equally well bymy method.

Several variations; in retort construction are suitable for carrying out my process, depending to a large extent upon the particular informaarrangement shown in Figure 5 can. be used.

Water stored in an elevated storage vessel 88 is admitted via line 8I- to flask 82 by opening stopcock 88. The rising water level in flask 82 will provide an air drive-to measuring cylinder I! through stopcock 84 and line 8Ii Stopcock 84 is off any passageway between line'8i and line 88 Cylinder n is provided with a stopper through which line 85 enters and a release tion desired. For example, Figure 2 illustrates the use of a separate steam generator as an external unit. A flask or other medium SO-is partially filled with water and is tightly stoppered, the stopper being provided with a safety tube BI and an outlet 52 in which is a three-way'stopcook 53 leading both to the outlettllbe 52 and a tube 54 leading to retort l0. Heating means (not shown) are provided to vaporize the water in flask 58. With this arrangement the steam isinjectedinto the retort under considerable pressure, since the generator is kept under a constant head of steam through .the useof safety tube 5|. Excessive pressure can be released by exhausting the steam into the atmosphere usin three-waystopcock 53. Whenever it is desired, stopcock 53 may be turned to direct the steam into the retort. In the event'that the sample should prove to be too compact to allow rapid penetration by the steam, thus building up pressures in the steam generator, the safety tube will permit the release of the pressure to the atmosphere. In using an outside steam generator,

turned to provide a direct passageway from flask.

82 through line 88 to. line 85, meantime shutting through line 81.

line 88 equipped with a clamp or other means for closure. Whenever the flask 82-becomes filled with water from line 8!, it can be drained by closing. stopcock 83 and by opening clamp 88 in however, it is impossible to determine the amount of moisture present in the original bit cutting in one operation, since there is no measured quantity of water converted to steam. In the event that the analysis is to be set up on a dry basis it will be necessary to make a separate determination for the amount of moisture content by any of the well-known methods on another portion of the wet drill cuttings, or the sample can be air dried prior to determination of the hydrocarbon content.

Figure 3 illustrates a retort that has for its adchanges to the apparatus should be obvious, and a line 88 and drain 98. The waterin cylinder ll I can be replenished at will by closing stopcock V 88, opening clamp 88, and turning stopcock 84 ninety degrees clockwise so that a direct passage is formed between lines 85, 81 and 8|. By using this arrangement measuring cylinder II can be placed at any level convenient for reading, since the water column from water container 80 to flask 82 provides the required head tov overcome thev pressure exerted bythe absorption meduim in column2l.

Although I have described the use of myapparatus employing carbon tetrachloride as an absorption medium, it should be understood that any suitable solvent can be used, particularly those mentioned previously. In some cases, however, the solvents are lighter than water, and therefore will float above the water layer. this event it will be necessary to withdraw the solvent and absorbed hydrocarbons from a point above the water level, or to withdraw the water prior to drawing off the hydrocarbon and solvent through line 35 to vessel 36. The necessary have not been illustrated.

Prior methods of extracting hydrocarbons from samples of earth formation have been confined chiefly to leaching or to the use of Soxhlet apparatus. When using either of these methods, and

particularly the leaching method, various porvantage simplicity of construction. Line 80 leading from measuring cylinder I1 is fabricated to pass directly through female joint SI of retort l0 and penetrate into the retort a limited distance. By opening stopcock 62 in line 68 water is added directly from cylinder I! to the retort. Since the retort is at an elevated temperature, the water is vaporized, flushing out the hydrocarbons still remaining within the sample. A variation of this type of retort is shown in Figure 4 which is designed to give a bottom steam delivcry. The water deliverytube 68 has been lengthened to extend almost to the bottom of the re tort passing through a sleeve 63 and perforated plate 64. The sample is Placed in the annular space between sleeve 63 and the retort wall and on topof the perforated plate. Water injected through water tube will strike the heated retions of organic vegetable matter are to be found in the solvent, thus masking to some extent the true hydrocarbon content of the sampledue tothe presence of oil and/or gas at deeper strata. The leaching method is also deficient in that not all of the heavy hydrocarbons in the sample may be absorbed in the solvent, particularly if soil most manufacturing centers, may offer dimculties in the way of obtaining an adequate supply for field laboratories. Moreover, it often happens that a part of the organic vegetable matter present may be decomposed, the strong heating causing destructive distillation and giving an erroneous yield of hydrocarbons. All of these shortcomings are overcome by the use of my invention. Substantially all of the hydrocarbons present are recovered by the combination of relatively mild heating and steam flushing, the loss of light or heavy hydrocarbons is reduced to a minimum, and contamination with organic vegetable matter is practically eliminated. In addition, since it is unnecessary to dry the sample before extraction, there is a saving in time as well as elimination of loss of light hydrocarbons, and if solvents heavier than water are employed, the water seal" effect of the water abovethe solvent prevents solvent loss. An additional advantage is that the water content of the sample can be determined simultaneously with that of the hydrocarbon content. Simplicity of apparatus and reagents also makes it admirably suited for field work.

Certain details, such as connections, supporting means, etc. have been omitted from the description and drawings for the sake of simplicity, and will be readily supplied by those skilled in the art wishing to practice my invention. Although I have illustrated my invention by reference to certain specific embodiments thereof, it should be realized that this is by way of illustration and not by way of limitation, and that my invention is to be limited only as set forth in the appended claims.

I claim: Y

1. The method for the determination of hydrocarbons in earth formations which comprises heating a sample of said earth formation sufficiently to vaporize at least a substantial part of said hydrocarbons, passing said vaporized hydrocarbons into a cooled water immiscible absorption medium whereby said hydrocarbons are absorbed, thereafter passing steam through said heated sample and into said absorption medium whereby hydrocarbons remaining in said sample are vaporized and absorbed in said absorption medium, condensing the steam in said absorption medium, and determining the amount of the hydrocarbons absorbed in said absorption medium.

2. The method for the determination of hydrocarbons in earth formations which comprises heating an undried sample of said earth formation sufficiently to vaporize at least a substantial part of said hydrocarbons together with any moisture present in said sample, passing the vapors from said heated sample into an absorption medium which is immiscible with water whereby said hydrocarbons are absorbed, thereafter passing steam through said heated sample and into said absorption medium whereby hydrocarbons remaining in said sample are vaporized and absorbed in said absorption medium, condensing in the absorption medium containing absorbed hydrocarbons all of the moisture and steam whereby all the water will separate from the absorption medium, and determining the amount of hydrocarbons absorbed in said absorption medium.

3. The method for the determination of hydrocarbon and moisture content in earth formations which comprises heating an undried sample of said earth formation sufliciently to vaporize at vaporized and absorbed in said absorption medium and said steam is condensed, determining by difference between the total condensed water and the steam added the moisture content of said sample, and separately determining the amount of hydrocarbons absorbed in said absorption medium.

4. The method according to claim 1 in which said samples of earth formation are drill cuttings taken at spaced intervals along a well bore.

5-. The method according to claim'l in which said absorption medium has a refractive index substantially different from that of the hydrocarbons from said earth formation whereby the hydrocarbons absorbed in said absorption medium are determined by comparison of the refractive index of said absorption medium and the refractive index of said absorption medium containing said absorbed hydrocarbons.

6. The method according to claim 1 in which said absorption medium is carbon tetrachloride.

7. The method according to claim 3 in which said steam is formed by vaporizing a measured quantity of water.

8. The method according to claim 1 in which said sample is heated to a temperature within the range of from about 250 F. to about 600 F.

9. The method for the determination of moisture in earth formations which comprises heating a sample of said earth formation sufliciently to vaporize at least a substantial part of said moisture together with any hydrocarbons present in said sample which are volatile at such temperatures, passing vapors from said heating through a cooled absorption medium for said hydrocarbons whereby said hydrocarbons are absorbed and said vaporized moisture condensed, passing a measured quantity of steam through said sample and into said cooled absorption medium to vaporize remaining moisture and recover it by condensation, and determining by the difference between the total condensed water and the measured amount of steam the amount of moisture present in said sample.

HENRY F. STURGIS. 

